This invention relates to a coil spring unit assembly, and more particularly to a coil spring unit assembly for use as a drop-in seat component.
In the assembly of furniture comprising coil springs, coil springs are variously mounted on or supported by wooden slats; steel slats, bars, or wires; or woven webbing or sheeting materials which require stretching and stapling to the frame and often require additional support from steel bands. The bottom ends of the coil springs are thus required to be attached to these support systems by means such as stapling, twisting coil ends into slots or over intersected wires, crimping, clipping or clinching. The top ends of the coil springs are commonly unitized by means of combinations of crimped wires and wire hooks; cross helicals; helical lacing wire; or pre-made grid material, requiring clipping or clinching. The coil tops are also commonly attached to a perimeter border wire by means of clips and/or by wrapping the ends of the top crimp wires around the border wire.
Assembling the spring unit by utilizing attachment clips or intertwining metal elements together is an expensive and tedious operation involving considerable costs in both material and labor. Furthermore, assembly in such a manner requires a degree of skill and expertise in utilizing the specific attachment hardware and tools required for securing the upper turns of the coil springs to the top grid structure. As a result of the specialized tools and skills required to attach the coil springs to the wire grid, the spring unit components and assemblies are often required to be manufactured at the spring manufacturer, which means that the unit must be shipped to the chair or furniture company only after it has been fully assembled by the skilled personnel at the spring company. Shipment of the fully assembled spring assemblies typically requires baling to compress the spring assemblies for economical transportation, which is very expensive; which requires the furniture manufacturer to invest in bale opening equipment; which can be hazardous; and which can lead to damaged product.